Technology Uses Liquid Salt for Emissions Scrubbing

Less than a year after patenting a process that could improve stripping greenhouse gasses from industrial emissions, a University of Alabama engineering professor has been granted another patent that uses a different solvent to accomplish the same goal.

Assistant professor of chemical and biological engineering Dr. Jason E. Bara’s latest patent uses a form of liquid salt that could be swapped with chemicals currently used to scrub harmful emissions, such as carbon dioxide, from industrial emissions.

In a different patent granted in August 2013, Bara proposed switching currently used chemicals with a class of low volatility organic molecules. That patent was licensed by Ion Engineering in August. It is all part of his research focus of showing different, and possibly better, ways to capture harmful emissions.

Nearly all commercially available scrubbing products use a liquid solution of water and amine, derived from ammonia, that contacts the stream, removing CO2 or other unwanted gases. The system patented by Bara would replace much of the water in the aqueous amine solutions with imido-acid salts, a negatively-charged group of organic solvents with almost no vapor pressure, or boiling point.

The patent, granted in March to the university, claims the chemical makeup of the imido-acid salts for use in capturing CO2 and other gases from natural gas and post-combustion emissions such as those from coal-fired power plants.

There are global efforts to reduce the man-made emission of greenhouse gasses that contribute to global warming by trapping the sun’s heat inside the atmosphere, including emission standards and financial penalties on excess emissions. The most common and most studied method is introducing monoethanolamine, or MEA, into natural gas or post-combustion emissions, a process that can capture about 90 percent of CO2 from flue gas.

The use of MEA to scrub flue gas is energy intensive since recycling the solution requires boiling it to desorb, or rid, the CO2 before recycling the MEA solution back into contact with the flue gas. The cost of the energy needed to use MEA in power plants, for example, would likely be passed onto consumers, Bara said.

Bara’s work shows that swapping most of the water in the process for other chemical solvents saves energy since the solvent can be regenerated without boiling large amounts of water, a cost and energy-intensive process. It also shows the solvent system can capture the same or more CO2 than MEA.